In the case of gear mechanisms in the drive-train of wind turbines simple servicing and maintenance are particularly important, because owing to their exposed position at the tip of a tower that can be up to 100 meters tall or more, the boundary conditions existing for wind turbines are exceptionally difficult. Furthermore, the size and mass of a typical gear mechanism in the drive-train of a wind turbine with a power of several megawatts are so large that even owing to the mass and size of the individual components, the effort and complexity involved, for example for the safe and efficient replacement of components are very substantial.
Known gear mechanisms in drive-trains of wind turbines often comprise a planetary gear stage on the drive input side and a number of spur gear stages on the drive output side, such that each transmission stage increases the rotational speed of the shafts in order to, starting from the slowly rotating rotor shaft of the wind turbine, finally produce higher rotational speeds at the generator which are suitable for electric power generation. In particular, the faster-running spur gear stages on the drive output side in such wind turbine gear mechanisms require regular servicing and more frequent maintenance work, involving the replacement of gear components.
DE 101 59 973 A1 describes a wind turbine gear mechanism having a planetary gear stage arranged on the rotor or drive input side and two spur gear stages arranged on the drive output or generator side. In this case, power branching to two intermediate shafts is provided in the first spur gear stage. The wind turbine gear mechanism designs proposed in DE 101 59 973 A1 comprise, among other things, a number of housing component joints in the housing for the spur gear stages on the output side. However, the gear mechanism housing portion of the spur gear stages is divided into so many housing portions that the manufacturing and assembly costs and complexity are comparatively high.
Besides the above, other systems also are known in which the central axes of two mutually parallel transmission shafts of a wind turbine gear mechanism are located in a common plane with a separation joint of the gear mechanism housing. This arrangement has the advantage that once the parts of the housing have been separated both of the transmission shafts can be fitted in the one separation plane. However, in the known arrangements of this type large wind turbines have two gear mechanism housing halves which are too heavy and/or too large to be separated and detached from one another in situ, i.e. in the gondola on the tower of the wind turbine. With such gear mechanism housing structures a separate crane is needed to enable the replacement of gear mechanism components, which lifts the components up from the ground. This entails considerable costs.